This invention relates to a system for indicating fuel consumption rate in a vehicle driven by an internal combustion engine through a multi-speed transmission, and particularly to such systems wherein fuel consumption rate is displayed for vehicle operation both in the highest transmission gear and in the next highest transmission gear.
There is known to be an approximately linear relationship between the vacuum pressure in the intake passage of a gasoline engine and the fuel consumption rate per distance travelled for the vehicle, when the vehicle is operating in the highest gear of its transmission. This relationship is substantially linear over a wide range of engine speed and load conditions. This range is an adequate range to provide fuel consumption rate information derived from intake pressure to a vehicle operator in order to enable him to achieve fuel economy during vehicle operation. While the range of linear fuel consumption rate indication does not include periods of high fuel consumption, for example when the vehicle is accelerating, or when the engine is idling, these engine conditions are generally not sustained over a long period of time and consequently do not have a substantial impact on overall fuel consumption. For practical purposes, it is sufficient to provide a display of fuel consumption rate for a gasoline engine driven vehicle over a relatively narrow range of engine operating conditions, corresponding, for example, to intake vacuum pressures of between two and six meters of a water column. Such consumption rate can be conveniently displayed in liters per one-hundred kilometers or other measure of efficiency.
The linear relation between fuel consumption and intake vacuum pressure is valid for only a single operating gear of the vehicle. If it is desirable to indicate fuel consumption rate for operation of a vehicle in other than the highest vehicle gear, for example, the next highest gear, a different linear relation between fuel consumption and vacuum pressure exists. Lower gears, for example, first and second gear, or reverse gear, in a four speed transmission, are generally used only for brief periods of time, and operation in these gears does not contribute significantly to overall vehicle fuel consumption. Therefore, there is no valid reason for displaying fuel consumption rate when these gears are being used.
It is an object of the present invention to provide a new improved system for indicating vehicle fuel consumption rate.
It is a further object of the invention to provide such a system which provides an indication of fuel consumption rate during vehicle operation in the second highest gear as well as during vehicle operation in the highest gear.
It is a further object of the invention to provide such a system which makes use of a single instrument for displaying the fuel consumption rate in the highest and second highest gear.